Soak the clams in a large bowl of cold water, and sort through them, discarding any shells that remain open or are cracked or smashed.
Put a pot of water on to boil. Add the salt to the water. Once boiling add your pasta and boil according to the directions on the box (about 8 minutes).
Meanwhile, mince the garlic, chop the shallots, and finely slice the parsley stalks. Roughly chop the parsley leaves and set aside.
Put a large pan with a lid on medium heat. Add oil, garlic, shallots, red pepper flakes, and parsley stalks. Fry for a few minutes until shallots are softened. Add a pinch of salt and pepper.
Add clams and pour in the wine and lemon juice and cover. Give it a good shake while covered to get the clams moving and steaming. Keep shuffling the pan around every so often until all the clams have opened. Turn off the heat. Get rid of any clams that haven't opened.
By now your pasta should be ready. Drain and add to the pan of clams along with the parsley leaves (reserve some for finishing the dish), lemon zest, and an extra drizzle of olive oil. Stir for another minute.
Add the zucchini noodles and stir gently until softened.
Finish with a sprinkling of parsley and serve.